essential [Pubmed|12682299], mutation is only possible in a ''[gene|4BD4CFB10700907DF1BBF3C9CFACAF573588E85F|ydiR]'', ''[gene|A8C606348C8C6FC3BB9786C06C9BFE9D3519A041|ydiS]'', or ''[gene|D36B91B3C8EAFEB80A7395C62A50A5F80B8CC5C5|ydjA]'' background (''i. e.'', in the absence of the BsuM DNA restriction system) [Pubmed|11751814]